On the origin of the story, consider that wire-mesh cages were at that time a standard feature for Zyklon delousing devices. See this photo of a Degesch circulation device in a Dachau delousing chamber.
Related to this, Graf mentioned a 1940 paper which must have included a similar description of a wire-mesh cage.
In order to accelerate the delousing of clothing, special chambers were installed that operated according to the so-called Degesch Circulation Procedure. In these chambers, the Zyklon-B cans were opened by means of a mechanism operated from outside. The pellets fell into a cage, onto which a fan blew warm air; this caused the swift evaporation of the hydrogen cyanide, and quickly spread the toxic vapors throughout the entire chamber (Peters/Wüstinger 1940).
Auschwitz: Eyewitness Reports and Perpetrator Confessions of the Holocaust by Jürgen Graf, p.77
Thank you Wetzelrad! Great posts and much appreciated. Also, thank you for pointing me at Holocaust Handbook 41. A collective appendix for the entire series would be useful. It's a lot to parse.
If I were to guess why no t4 personnel were chosen to perform gassing that had experience with gassing, it would be because THERE WERE NONE.